1. Field of the Invention
The present invention relates to an electronic device having a first electrode and a second electrode disposed on the front surface of a semiconductor substrate, wherein the first electrode and the second electrode each comprises at least one epitaxial graphene monolayer. More specifically, the invention relates to an integrated circuit with silicon carbide (SiC) as semiconductor substrate and graphene layers on that substrate.
2. Description of the Related Art
Monolithic integrated circuits are electronic circuits manufactured on one semiconductor substrate, comprising connected electronic devices like transistors, diodes, capacitors and resistors. Today, integrated circuits are mainly manufactured on the basis of Silicon (Si). However, other semiconductor materials may have advantages for specific application areas like high frequency or high power applications.
Silicon carbide for example with a band gap of approximately 3 eV has advantages for switching and controlling high power. Current technical applications of Silicon carbide are based on the principle of MOSFET's, JFET's or bipolar transistors. For such devices the silicon carbide substrate is doped with p-type and with n-type impurities.
In the WO 2005/001895 A2 an electronic device is disclosed, having a silicon carbide substrate and at least two graphene electrodes disposed on the surface of the substrate. In particular a transistor element is shown constructed by a graphene source electrode, a graphene drain electrode and a graphene gate electrode. These electrodes are disposed on the surface of the silicon carbide substrate. The drain electrode and the source electrode are bridged by a thin graphene strip. The gate electrode adjoins the thin graphene strip. Using the field effect the graphene in the thin strip is gated by applying a voltage to the graphene gate electrode.
In addition, the WO 2009/158552 A2 discloses an electronic device constructed by graphene electrodes disposed on the surface of a silicon carbide substrate. The graphene of the electrodes is chemically modified. Graphene itself is gated as a thin strip also using the field effect.
Graphene as a single layer or monolayer of graphite shows an excellent carrier mobility as well as an excellent ampacity. However, graphene exhibits no band gap; graphene is not a semiconductor. Graphene shows metallic conductivity. Due to the lack of a sufficiently large band gap, gating the graphene will therefore not result in an acceptable on/off-ratio of respective active devices. The on/off-ratio is increased when using a thin graphene strip or by chemical modification of the graphene layers, where both methods result in disadvantages like the requirement of cryogenic operation temperatures or slow switching frequencies.